You trap snails using vegies - After you back off on feeding. They are a symptom, not a disease. Over feeding is the disease.
Cut a thick slice of zucchini or cucumber. Stick a fork in it so it will stay on the bottom. In the morning, or every few hours during the day, pull it out and scrape off the snails. Replace and repeat. The goal is to get them under control, not rid the tank entirely.
For some of the carnivorous pests, strips of fish work well.